What is this module?

1971 Demon 340 show car, with this module on the inner fender, I believe it may be some sort of alarm or theft deterrent. Any ideas what it might be? There's a note in the console from the previous owner that the car is alarmed and if it won't start push the button...I can't find any buttons and the previous owner is not available! I realise this is a long shot but thanks in advance.

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